Calutron receiver



3 Sheets-Sheet 1 Filed May 14, 1946 INVENTOR. Sidney Wfiarnes.

C Aug. 25, 1959 S. W. BARNES CALUTRON RECEIVER 3 Sheets-Sheet 2 Filed May 14, 1946 INVENTOR. Sidney WBarnes.

Aug. 25, 1959 s. WJBARNES CALUTRON RECEIVER Filed May 14, 1946 3 Sheet s-Sheet 3 llllllllllllllnllal.

INVENTOR. Sidney WBamcS.

BY Waw United States Patent CALUTRON RECEIVER Sidney W. Barnes, Rochester, N.Y.,v assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application May 14, 1946, Serial No. 669,481

7 Claims. (Cl. 250-413) The present invention relates to apparatus for separating. charged particles, such as ions, by utilizingthe magnetic mass spectrum thereof.

Oneform of apparatus which has been used for this purpose comprises the combination of a partially evacuated closed vessel and a magnetic field of such strength as to constrain uniform velocity ions projected within the vessel to motion on circles having radii which are a predetermined fixed function of the momentum of the ions. By such means it is known that ions having a common origin and traveling different paths of equal curvature will, due. to geometrical focusing action, substantially pass through a common region after 180 of travel.

When the paths of the ions are divergent by half angles greater than about 4 it is generally desirable to perturb the magnetic field in the middle half of the travel of the beam to improve the focus. This may be done with magnetic shims.

In order for apparatus of the above type. to have practical utility as a means for making isotopes available in quantity, it is necessary to collect separately the ions differing in mass i.e., the difierent isotopes", so that they may be recovered to provide materials having greater proportions of certain isotopes than occur in nature. While the apparatus of the present invention is not limited to the separation of the isotopes of any one element, it must be of necessity be specially adapted for the masses involved, and in order for its principles to be clearly understood, the invention will be described as embodied in apparatus adapted for the separation of the uranium isotopes having atomic weights 235 and 238, the isotope having an atomic weight of 234 being ignored.

It is a primary object of the present invention to. provide relatively simple receiver means for collecting isotopes which have been electromagnetically separated.

Another object of the invention is to provide such receiver means adapted for the separate recovery of collected isotopes.

A further object of theinvention is to provide such a receiver which will furnish information for control or regulating purposes. 7

A further. object of the invention is the provision of av receiver such that the isotope which is not being concentrated is collected in substantially pure form and removed from the cycle.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawings. The scope of the invention is pointed out in the appended claims. r

In accordance with the present invention in its preferred form the receiver is adapted for use in isotope separating apparatus using magnetic shims and enriched feed i.e., uranium having a larger proportion of U235 than in nature, and provides electrically correct readings for monitoring purposes. It is a more efficient collector of the 238 isotope than of the 235 isotope and thus the unwanted isotope U238 is collected in the maximum amount and may be removed so that the feed for recycles becomes richer in the desired isotope, U235, until an equilibrium value is reached. To take advantage of this fact and to give as long a life as is reasonably desirable, the pocket for receiving the U238 is made deep, and the wall separating this pocket from the pocket for receiving the U235 is at such an angle that none of the U238 beam. hits it directly. The U238 pocket therefore has perfect electrical resolution and this theoretically should permit accurate maximization of the total ion beam;

For convenience of description and in conformity with common usage, the ion beam which is predominately U238 will be referred to as the Q beam, and the pocket intended for its reception will be called the Q pocket. Similarly, the ion beam containing the U235 will be referred to as the R beam and the pocket intended for its reception will be called the R pocket.

In the drawings:

Fig. 1 is a diagrammatic view in section of an isotope separating apparatus incorporating the receiver of the invention;

Fig. 2 is a view in perspective and with part torn away of a receiver constructed in accordance with the preferred embodiment of the invention; and

Fig. 3 is a front view partly in section of a fragment of the receiver shown in Fig. 2.

Referring to Fig. 1, there is shown a closed vessel 10 positioned in a strong magnetic field provided by a magnet one pole piece 11 of which is shown. The vessel 10 provides a space within which electromagnetic separation of ions may take place and is preferably highly evacuated although the presence of a small amount of gas is desirable under some circumstances to avoid so-called space charge effects.

Within the closed vessel 10 and also within the region of influence of the magnetic field produced by the pole piece 11, there is provided a source 12' of ions, of a material the isotopes of which it is desired to separate, which in conjunction with an accelerating electrode 13 serves toproject in a direction normal to the magnetic field a stream or beam of high velocity ions. The accelerating electrode 13- is made negative with respect to the ion source 12 by means of anysuitable direct current supply which preferably is adjustable. As is well known, these accelerated ions in traversing the magnetic field will beforced to follow circular orbits which results in the formation of the magnetic mass spectrum of the ions after approximately of travel from the accelerating electrode 13-. If, as is here assumed, the ions consist primarily of the two isotopes of uranium, the 238 ions will follow orbits having the curvature of a path Q and the 235 ions will describe orbits of stronger curvature indicated by a path R.

According to the embodiment shown in the drawing, a receiver 14 positioned at the 180 point in the travel of'the Q and R beams has two pockets Q and R adapted to receive the Q and R beams, respectively. A wall 15 of the R pocket separates the two pockets and cooperates with a face plate 16 to define the entrance slot to the R pocket. The entrance slot to the Q pocket is defined by the wall 15 and an electrode 17. A second face plate 18 determines the exposed area of the electrode 17 and serves to collect particles scattered by the electrode 17". The R pocket, the Q pocket and the electrode 17 are each electrically isolated to the end that the deionizing current to each may be individually measured as by meters 19, 20 and 21, respectively. It will be noted that the wall 15 of the R pocket and the electrode 17 form an inverted truncated V, whereby all ions entering the entrance slot to the Q pocket which is formed between wall 15 and electrode 17 actually impinge on the walls or bottom of the Q pocket and are metered by meter 20.

The wall 15 is so shaped and positioned that the side facing the Q pocket is not hit directly by any of the Q beam and the side facing the R pocket i in the path of all of the ions entering the R pocket. It will be evident that the R pocket has a slightly greater electrical Width than mechanical width due to the finite thickness of the top of the wall 15 which rejects ions into the tank 10. These rejected ions appear in the reading of the meter 19 however.

With the above described structure it is possible for an operator to know the position of the Q beam by the readings of the meters 20 and 21 and in this way ascertain whether or not the accelerating voltage is properly adjusted. The reading of the Q pocket meter 20 furnishes information with respect to the efficiency of the ion source 12.

Since usually the R beam is much less intense than the Q beam, the life of the Wall 15 is lengthened considerably by having it arranged so that it is bombarded by only the R beam. This serves to lengthen the life of the receiver because the dividing wall between the two pockets is the least robust part and the position of its leading edge is quite critical.

In Figs. 2 and 3 the receiver 14 is shown in greater structural detail and with like reference characters applied to like parts. It will be noted that the face plates 16 and 18, the wall 15 and the electrode 17 are shaped to define curved entrance slots to the Q and R pockets. The particular curvature of these slots depends upon the perturbation of the magnetic field and for any particular apparatus will be made to coincide as nearly as possible with the foci regions of the Q and R beams. The bottom of the Q pocket has footscraper blades 22 for the well known purpose of retaining ions entering the Q pocket. The Q pocket, the R pocket and the electrode 17 are supported in and insulated from the receiver 14 in any well known manner. All of the parts of the receiver which are subject to bombardment of the ions are preferably made of carbon to impart durability. Additionally the entire R pocket is preferably of carbon so that it may be asked to facilitate recovery of the U235 it collects.

The details of assembly and mounting of the various parts are subject to wide variation and have not been described in detail since any one skilled in the art can from the above description readily construct a receiver incorporating the invention.

I claim:

1. In isotope separating apparatus in which ions of the different isotopes are caused to travel through different regions approximating foci in accordance with the magnetic mass spectrum thereof, means for establishing the magnetic mass spectrum of the respective isotopes as closely adjacent beams of ions at the foci regions, a re ceiver comprising means forming two collecting pockets having openings corresponding in size and position to said foci regions, and a dividing wall between the two pockets arranged at an angle such that substantially all of the ions of the less abundant isotope entering one of the pockets strikes one side of the wall directly and substantially none of the ions entering the other pocket strikes the wall directly.

2. In isotope separating apparatus, means for establishing the magnetic mass spectrum of isotopic ions as respective ion beams, receiver means comprising means forming two adjacent pockets disposed in the path of the respective ion beams and separated by a single wall the leading edge of which shadows the side of the wall facing the pocket positioned for the reception of ions of the most abundant isotope.

3. In apparatus for the electromagnetic separation of two isotopes of an element, means for establishing the 5 magnetic mass spectrum of the two isotopes as closely adjacent beams of ions, receiver means having two entrance slots leading to two pockets formed of electrically isolated walls, said slots being positioned in the respective paths of said beams, a Wall of the pocket positioned to receive the ions of the less abundant isotope defining one side of the entrance slot to the pocket positioned to receive the ions of the more abundant isotope and being slanted upwardly toward the pocket positioned to receive the ions of the more abundant isotope so that none of the ions striking the Wall enter the pocket positioned to receive the more abundant isotope, whereby the deionizing current to the Walls of the pocket positioned to receive the more abundant isotope is an accurate indication for monitoring purposes.

4. In isotope separating apparatus, means for establishing the magnetic mass spectrum of isotopic ions as respective ion beams, receiver means comprising means forming two adjacent pockets disposed in the path of the respective ion beams and separated by a single wall the leading edge of which shadows the side of the wall facing the pocket disposed to receive ions of the more abundant isotope, the pocket so shadowed having a greater depth than the pocket disposed to receive ions of the less abundant isotope.

5. In isotope separating apparatus, means for establishing the magnetic mass spectrum of isotopic ions as respective ion beams, receiver means comprising means constructed of electrically conductive material forming a pocket positioned to receive the ions of one isotope,

an ammeter connected to said pocket for indicating the de-ionizing current to said pocket forming means, and means disposed over said pocket and forming an entrance slot to said pocket, said last named means being electrically insulated from said pocket forming means and having two side wall portions forming an inverted truncated V over said pocket, the truncated end of the V forming the entrance slot to said pocket.

6. Apparatus as claimed in claim 5, wherein said two side wall portions are also made of electrically conductive material and are insulated from one another.

7. In apparatus for the electromagnetic separation of two isotopes of an element having a greater proportion of the heavier isotope, means for establishing the magnetic mass spectrum of the two isotopes as closely adjacent beams of ions, receiver means including means forming two electrically isolated pockets positioned for separately receiving the respective ion beams and means forming two entrance slots to the respective pockets, the pocket positioned to receive the more abundant heavier isotope being deeper than the pocket positioned to receive the less abundant lighter isotope.

References Cited in the file of this patent UNITED STATES PATENTS Oliphant et al.: Proceedings of the Royal Society of London, vol. 146A, 1934, pp. 922929.

Smythe et al.: Physical Review, Feb. 1, 1937, vol. 51, pp. 178-182. 

